Which of the Following Is an Example of Confirmation Bias

Which of the following is an example of confirmation bias?

A) James hypothesizes that extroverts will have a bigger circle of friends on social media. He sends a personality questionnaire to all his followers on twitter measuring their level of extraversion and the number of friends they have on Facebook.
B) Sophia hypothesizes that increased exposure to sunlight results in an elevated mood. She recruits only participants who are living in a sunny climate and sends them a questionnaire that measures mood.
C) Kyle hypothesizes that daily chocolate consumption decreases stress levels. He recruits twenty participants and randomly assigns ten participants to one of two conditions: daily chocolate consumption or no chocolate consumption. After a week, he measures their stress levels.
D) Jeremy hypothesizes that listening to Mozart from infancy will result in a child developing better cognitive skills. He recruits mothers who report that listening to Mozart has beneficial effects on their infant and measures the improvement of the children's cognitive skills over time as reported by the mother.